Bragging again oh yeah, I have the same problem
D

 

I would love to see good quality vids if you have some

 

I'm pretty sure they are all on youtube, including the one with the evo spin out

 

http://www.youtube.com/watch?v=aPo_jstgvMs

http://www.youtube.com/watch?v=dVLQRnDHgvU

There are a couple...

Mike

 

4 WD has it’s benefit’s. I can drive my 996TT hard with confidence. Driving the 2 WD 7GT2 hard, it wants to send me in the forest every time.

 

Mike,
Nice vids. Dog you got skills.
Duane

 

Impresive, Mike. Good setup and good driver. You passed Ferraris easily. I thought they are fast ones on track.

 

This was from two years ago with what I would couch as poor suspension settings... I've got a bunch of training (instructing has really helped me become a better driver as well) and suspension improvements. I expect to have much more impressive videos to share later this season.

Mike

 

There are really two factors in this equation. The first is "handling" in the sense of outright grip. This is a simple engineering function of weight, CG, roll centers, dynamic camber changes as a function of suspension movements, tire width and compound, etc. There's nothing you can "do" with a GT3 that you couldn't do with a 996TT as they are basically the same cars (assuming you get rid of the 4wd), with the one exception that you have 150 to 200lbs more turbo-related plumbing on the turbo at the wrong end of the car.

So at the same weight with the same tires, the mechanical grip of the turbo will be slightly less (GT3 can use it's front tires more) due to the extra weight at the back.

The second part of the equation is control. How well can you dynamically control that grip in the middle of a corner as the car moves around? This is far more difficult in a turbo and it doesn't matter how well "setup" and efficient your turbos, plumbing, intercooling, etc. It isn't so much a function of lag in the traditional sense as most of the time on the track you are above 4000rpms and get very quick spooling. Many people make the mistake of assuming quick spool = throttle modulation precision. It doesn't.

In a turbo, throttle modulation (between vacuum and boost) is much more difficult because it's a function of HUGE changes in airflow through the intake track. In any car with the throttle fully closed, you get nearly 1bar of vacuum in the intake because the pistons are sucking hard and the throttle isn't letting much air in. With the throttle fully open, in NA you are at a slight vacuum. With a turbo at full boost, you are probably above 1bar of positive pressure.

The pressure differences in a turbo are roughly 2x what they are in an NA car, so the swing from positive to negative pressure (and corresponding torque) is much more dramatic. This is why turbos have all these exotic blow-off valves, etc. and is magnified by the fact that even the best turbos don't spool instantaneously, have to build intake and intercooler pressure, etc.

This comes into play when you make mistakes and have to make fairly dramatic line change using throttle corrections. You can get an NA car settled and back on line much more quicly because you don't have to cycle through pretty massive intake manifold pressure, and torque, changes.

Imagine you get on the throttle mid-corner a bit too early in a turbo, have to let off a bit, and then get back on it. Say you are close to the edge and the rear wheels can take 250ftlbs, but no more. You have to go from 250ftlbs to close to zero back to 250ftlbs in about 1 second. NA, you give a medium lift and drop to exactly the point where the front-end grips again and go right back to exactly the right spot on the throttle/torque curve. With a turbo, you have to blow-off boost, cycle into vacuum, respool, build boost again and then hit the torque target just right while building boost dramatically without overshooting with a throttle that is roughly 2x as sensitive in terms of manifold pressure with this whole equation.

Umm, that should be easy...

But forget theory, the best explainations are always objective, the GT2 has almost a 20% power to weight advantage over the GT3 and is less than 2%!! faster around the Ring.

 

Diminishing returns. You can't compare weight to power directly with ring time discrepancies on a direct level. 20% weight/power does not equal 20% faster lap time. It's a whole lot harder to shave 20% off a lap time than 20% in weight to power.

I do agree about throttle modulation precision though. But faster spooling is still better than slower, especially when you are not perfectly geared for the track you are on. If you can't go down a gear because it kills too much speed, turbos that spool faster at lower RPM's will make a huge difference.

 

Impresive driving Mike.Nice videos,we would like to see some more.

 

Actually, you can. I just didn't want to go insane geek in the last post. If you run a regression of lap times vs. p/w ratios of multiple porsches you get a really accurate formula:

(kg+100)/power)*14 (constant)+410(seconds)

So a GT3 is 1500kg (100kg for driver and fluids) * 14 + 413 = 7:41 and it runs a 7:42.

Use the same math for a GT2 and it should run 7:34 which is what it runs; completely disproving my last post.

All hail the GT2 as it's just as fast as a GT3 would be with the same NA power!

 

What does the 14 constant represent?

Simple math for the time of the GT2 is 452 seconds. (7 X 60) + 32

Simple math for the GT3 is 462 seconds. (7 X 60) + 42

10 seconds difference is 2%.


20% difference in time would be 369 seconds which would be 6 minutes 9 seconds.

You are making it too complicated.




Also increasing weight/power without increasing grip levels through contact patch, tire compound or downforce is not going to represent and equal amount of time reduction. The GT2 does not have stickier tires to use more of that power on exit.

This is why adding hp is not the most efficient way of making a car faster. Increasing tire grip through the compound always results in the biggest increase initially.

 

This thread is going in a direction I like, im all ! I think we are thinking on the right path. The reality is these are two completely different purpose built cars that really are not apples to apples. The vids are great! fantastic driving. I want to point out something, and I promise you I'm not making excuses, to me the track seemed like it had very comfortable straights most of the time (am I right?). Some interesting corners, but nonetheless. That really is where the turbo will come out and stretch its legs. Around the corners I feel you can't put power down as you could understeer- that is where the GT3 has the edge. Now please don't miss understand me Mike, I think YOUR car seems set up very tight compared to other vids I watched. At the end of the day it comes down to preference, do you want to redline at 8200 (996) 8400 (997) not blast through the straights, lighter etc. or freakishly fast T, heavier GT car with great potential once setup correctly. Either way with prices so similar, there are no losers here - lets keep this going

http://www.youtube.com/watch?v=CkrCtRHCFuw

http://www.youtube.com/watch?v=oUOPD3KmlIM

 

I like to read.....



just sayin